When you see a comment, status, picture, etc. that you really like, instead of clicking the "like" button once, out of sheer excitement you click the "like" button three times. It isn't a double like, for if you clicked the "like" button twice, it would merely "unlike" the comment, status, picture, etc. When you perform a triple like, you must immediately comment and let the person know that you have triple liked something of theirs.

John: *on Facebook, finds something of interest* Dude, this picture is so epic of us!

Tony: *replying* I know! That was the greatest vacation ever!

John: I made so many good memories there,
I gotta triple like this picture!